1. Field of the Invention
The present invention relates to solutions of polyimide-forming substances, containing
A) aromatic or partly aromatic polyamines and PA1 B) amides or a mixture of esters and amides of aromatic or partly aromatic tetracarboxylic acids. PA1 A) aromatic or partly aromatic polyamines and PA1 B) amides or a mixture of esters and amides of aromatic or partly aromatic tetracarboxylic acids.
The present invention furthermore relates to the use of such solutions for the production of coatings and of articles coated with polyimides, and coated articles.
Aromatic polyimides are as a rule insoluble in conventional organic solvents. In general, solutions of the more readily soluble polyamidocarboxylic acids were therefore used as polyimide-forming intermediates for polyimide-forming coatings. The polyimides then form from these intermediates on drying, for which temperatures of up to 400.degree. C. are used.
Disadvantages of the polyimide-forming polyamidocarboxylic acid coatings are their very high viscosities in relation to the solids content. This makes them more difficult to process and requires high dilutions.
Considerable disadvantages arise in applications in microelectronics where polyamidocarboxylic acid coatings are used as planarizing layers in the microelectronic structures, high concentrations in conjunction with low viscosities being required for good planarizing.
Furthermore, polyamidocarboxylic acids have a short shelf life since they tend to undergo self-hydrolysis and premature imide formation. Most polyamidocarboxylic acid coating materials therefore have to be stored in a freezer.